Pretty much the same as any ZTR. First you got raise the rear up and put jack stands under each rear corner. Note this must done a solid surface and not just your yard. This is because you will need to work under the mower.
Then the electric PTO clutch has to be removed. After this you will have access to the drive belt area. One tool you will need is a 1/2 square drive pull bar and a long extension as this how relieve the spring tension the moving idler to get the belt off an on. The rest is fair straight forward as feed the belt around the pump motors and the engine drive pulleys. Just be careful working under the mower as it can fall and crush you if not properly supported.
When reinstalling the PTO use antiseize compound on the PTO shaft and torque the PTO clutch retaining screw to 55 ft/lbs while making sure the anti-rotation device is properly installed in the PTO clutch.